1. Field of the Invention
The present invention relates to a sheet package production system for producing a package containing a stack of sheets.
2. Description of the Related Art
X-ray films or the like are produced by cutting a roll of photosensitive material into sheets of predetermined length, stacking a plurality of sheets, placing a protective cover on the stack of sheets, and inserting the sheets with the protective cover into a light-shielding bag, which is sealed and shipped as a packaged product.
The production of such sheets requires many complex processing steps to be performed. It has been highly difficult to automate all the processing steps for efficient production of the sheets. If the sheets are made of photosensitive material, e.g., if the sheets are photographic films, then since all the processing steps need to be carried out in a light-shielded environment, the processing steps become more complicated.
Specifically, a protective cover to be placed on a stack of sheets is folded so as to surround the sheets. The protective cover is folded by a robot, which is considerably expensive because it needs to make complex motions to fold the protective cover. If the protective cover is supplied in a folded shape, then it tends to cause trouble, e.g., its folded edges are likely to be caught in the sheet package production system upon feeding movement therein, and the folded protective cover is liable to take up a large area in the sheet package production system.
The efficiency with which to produce sheets may be increased by feeding sheets at higher speeds between various processing stations of the sheet package production system. However, sheets may not be fed at higher speeds in certain instances. For example, if a stack of sheets prior to be being inserted into a light-shielding bag is to be fed at a higher speed, the stacked sheets tend to collapse due to an abrupt increase in the speed when the sheets start being fed.
One solution is to start feeding the sheets at a lower speed and then feed the sheets at a progressively higher speed. However, the feed mechanism for feeding the sheets may not be controlled according to such a feed speed pattern. Specifically, processing stations positioned respectively upstream and downstream of the feed mechanism may not necessarily operate in synchronism with each other. For example, while a sheet is being fed at a lower speed in the processing station downstream of the feed mechanism, another sheet may be fed at a higher speed in the processing station upstream of the feed mechanism.
In the sheet package production system, a number of packaged products are stacked in a magazine and fed for efficiently processing the packaged products without taking up an increased space. If the packaged products are inflated by air, the stacked packaged products tend to collapse while they are being fed. Furthermore, unless a suitable amount of air is removed from the packaged products, the sheets in the packages are liable to move and be scratched or otherwise damaged. If, on the other hand, an excessive amount of air is removed from the packaged products when they are sealed, then since the light-shielding bag is held in intimate contact with the sheets, a portion of the sheets may be sealed together with the light-shielding bag at the time a front or rear end of the light-shielding bag is sealed, resulting in defective packaged products.
It is a general object of the present invention to provide a sheet package production system which is capable of producing packaged sheets efficiently in an automated production process.
A major object of the present invention is to provide a sheet package production system which is capable of reliably and efficiently supplying a protective cover for sheets without causing trouble.
Another major object of the present invention is to provide a sheet package production system which is of a relatively small size and capable of reliably placing a protective cover on sheets, and which is highly versatile in that it can easily handle sheets regardless of modifications of specifications thereof.
Still another major object of the present invention is to provide a sheet package production system which is capable of feeding stacked sheets efficiently without allowing the stacked sheets to collapse, and which is also capable of feeding stacked sheets irrespective of the timing of processing the sheets before and after the sheets are fed.
Yet another major object of the present invention is to provide a sheet package production system which is capable of appropriately drawing air from a package that contains stacked sheets, efficiently feeding the packaged sheets without allowing the sheets to collapse, and preventing defective packaged products from being produced.
Yet still another major object of the present invention is to provide a sheet package production system which is capable of folding a package reliably into a compact shape through a simple arrangement, and preventing defective packaged products from being produced.
A further major object of the present invention is to provide a sheet package production system which is capable of stacking packages reliably and quickly through a simple arrangement, preventing sheets housed in packages from being damaged, and handling packages of various sizes.